1. Field of the Invention
The present invention concerns a method for image data acquisition of a region of interest in a subject with a magnetic resonance device.
2. Description of the Prior Art
In the acquisition of image data with a magnetic resonance device, a number of artifacts are known that can occur when the image acquisition parameters are not ideally selected. In particular, an artifact known as aliasing can occur with regard to the determination of a field of view (FoV). This occurs when a field of view was selected in the phase coding direction so that a portion of the subject to be acquired (for example a patient body) is arranged outside of the field of view. Such artifacts can occur in the partition direction even if no slice selection pulse is used, but is barely possible in practice. The field of view in the phase coding direction (and possibly in the partition direction) is accordingly not selected based on the diagnostic requirements, but is instead set so that the requirements of k-space scanning are satisfied.
To solve this problem, it is known to select the field of view so large in principle that every conceivable subject to be acquired in the phase coding direction is completely encompassed by the field of view. The field of view is frequently manually determined, and an experienced user can estimate how the aliasing artifacts might appear and whether the region of interest is also safely free of aliasing. Uncertainties and consequently measurements of images with aliasing in regions to be diagnosed can occur in the case of less well-trained personnel or less experienced personnel, such that the image acquisitions must be repeated.
Due to the manual selection of the field of view, in the known methods it is additionally typical to select this field of view for only one slice of a measurement protocol, and then to apply it to all slices so that ultimately a field of view is created that is dimensioned larger for most slices, without this being necessary. This therefore leads to the situation that the user is not expected to input the field of view for every single slice (in particular in the phase coding direction) nor the position in the slice plane.
In the procedure that is typical today, a user accordingly defines the field of view manually for each examination step. In the event that the field of view is selected smaller than the subject and aliasing is to be anticipated, for the most part it is ensured using a test measurement that the region of interest (in particular an organ to be depicted) is free of aliasing. These test measurements are repeated until the desired goal is achieved. This is time-consuming and requires the acquisition of a plurality of additional measurement data.
In the methods available today, it is not possible for the user to adapt the field of view of a slice stack or of all slice planes of a protocol individually. Although isolated measurements are known in which slices are measured with a different field of view in different protocols, such a procedure significantly lengthens the examination, in particular when these are measurements in which a patient must hold his breath.